Screw locking device



April 20, 1965 KlNlCHl ITO 7 1 SCREW LOCKING DEVICE Filed o t'; 49, 1962 a Sheets-Sheet 1 INVENTOR.

P 'ZO, 1965 KINICHI ITO 3,

SCREW LOCKING DEVICE Filed Oct. 19, 1962 2 Sheets-Sheet 2 IN VEN TOR flaw J; m 90M United States Patent 3,179,142 SCREW LOCKING DEVICE inichi Ito, 498 S-chome Kaijincho, Funahashi, Chiba Prefecture, Japan Filed Oct. 19, 1962, Ser. No. 231,676 Claims priority, application Japan, Dec. 12, 1961,

1 Claim. (Cl. 151-25) This invention relates to devices for locking of screws.

In order to prevent screw fastened parts from being loosened by vibration or the like, the rotation of the bolt or nut has been prevented by using a spring washer, double nuts or other complicated device. The present invention provides a new device whereby the loosening of screws can be very positively prevented in a simpler and cheaper manner.

An object of the present invention is to provide a device for simply and positively preventing screws from being loosened by vibration or the like.

A further object of the present invention is to provide a cheap and easily operated device for preventing loosening of screws.

The present invention provides a screw driver of a special form to be used for the screw locking device.

In the accompanying drawings;

FIGURE 1 is a partly vertical sectional elevation of an embodiment of a screw locking device according to the present invention.

FIGURE 2 is a plan view of the device of FIGURE 1.

FIGURE 3 is a perspective view showing the fitting of the locking device with a special driver.

FIGURE 4 is a magnified sectional view on lines A-B, C-D, EF and G-H in FIGURE 2.

FIGURE 5 is a sectional view on line 1-] in FIGURE 4.

FIGURE 6 is a view for explaining the operation of the device of the present invention.

FIGURE 7 is a vertical sectional view showing another embodiment of a screw locking device according to the present invention.

, FIGURE 8 is an elevation showing another embodiment of a special driver employed in the present invention.

FIGURE 9 is a developed diagram showing the formation of the edge of the driver shown in FIGURE 8.

With reference to the drawings, in FIGURE 1, a bolt 2 is fitted and inserted in a body 1 to be fastened and is fastened with a nut 3. A conically sloping surface 4 is formed on the edge of the threaded aperture of the said nut. A steel ball 5 is fitted between the said sloping surface 4 and the walls of the adjacent groove of the screw thread of the bolt. FIGURE 3 shows an example of the method of fitting the steel ball. First of all, a steel ball 5 of a proper size is set between the conical slope 4 of the nut 3 and the side of the bolt 2. Then, a screw driver 7 having a conical part 11 at the outside of the forward end of a cylinder of such inside diameter as just fits the bolt 2, and having a concave groove 6 in the end is fitted on the projecting part of the bolt 2 as shown by the arrow at. The steel ball 5 is engaged in the said concave groove. The said driver 7 is then rotated in the same direction as the fastening direction of the nut 3 as indicated by the arrow [2. That is to say, in FIGURE 4, the solid line and the chain lines X, Y and Z show the crosssections on lines A-B, CD, E-F and 6-H, respectively, in FIGURE 2. However, if the steel ball 5 is set on the line C-D in FIGURE 2 as shown by the chain line 5', in this position, the top part 8 of the screw thread of the bolt 2 will be opposite the peripheral edge 9 of the slope of the nut, the distance between them will be considerably smaller than the diameter of the steel ball 5 and therefore-the steel ball 5 will be arranged perfectly above the nut 3 as shown by the chain line 5' in FIGURE 4 without fitting in the bottom of the screw thread. However, if the steel ball is fitted in the concave groove 6 of the screw driver and is moved to the part of the line E-F in FIGURE 2 by rotating the driver, in this part, as shown by the chain line Y in FIGURE 4, the top part 8 of the screw thread will move downward, the distance between the next top part 10 and the peripheral edge 9 will be larger than the diameter of the steel ball 5 and therefore the steel ball will begin to fit in between the slope 4 and the bottom of the screw thread as shown by the chain line 5". shown by the solid line, the steel ball 5 will perfectly fit in between the bottom of the screw thread of the bolt 2 and the slope 4. If the screw driver 7 is further rotated from this position, the screw thread will be as is shown by the chain line Z and'the space enclosed by the slope 4 and the bottom of the screw thread will be so small as to be unable to contain the steel ball. steel ball 5 will stop in the position shown by the solid line. In this position, the straight line 1 showing the inclination of the wall of the screw thread and the straight line m showing the inclination of the slope 4 of the nut will intersect each other at a point 0 outside the bolt 2 and therefore the said steel ball will be positively engaged and held between the walls of the screw thread and the slope 4 of the nut without any fear of dropping.

If the steel ball 5 is strongly pressed in between the slope 4 of the nut 3 and the walls of the screw thread of the bolt2 as described above, for example, by using such tool as the screw driver 7 shown in FIGURE 3, the nut 3 will be pressed as shown by a vector v in FIGURE 4. Therefore, due to this force, the contact pressure on the left side in FIGURE 1 of the bolt and nut will increase to prevent the nut from being loosened. Further, if, due to vibration or the like, the nut 3 rotates as indicated by the arrow C in FIGURE 5 and tends to become loose, though the steel ball 5 is in contact with the slope 4 and the screw thread of the bolt at the points p, q and 1' (see FIGURE 4), as a pressure is applied to the points p and q by the rotation of the nut, the steel ball 5 will roll with the said points p and q as fulcra. Therefore, if the point p on the slope 4 rotates to the point S, the'steel ball 5 will move to the position of half the rotating angle or the position shown by the chain line 5".

In FIGURE 6, the parts on the lines A-B, K-L and M-N in FIGURE 5 are shown by the solid line and the chain lines W and U, respectively. As the point p on the nut 3 rotates to the point S (see FIGURE 5), the cross-sections of the bolt and nut in this position will be represented by the chain lines U. On the other hand, as the steel ball 5 moves to the position of the chain line 5", the thread wall of bolt 2 in this position will be in the location of the chain line W. Therefore, as shown by the chain line 5" in FIGURE 6, the steel ball 5 will project out of the space enclosed by the slope of the nut a part of which is shown by the chain .line U and the screw thread of the bolt shown by the chain line W. That is to say, if the nut rotates and tends to loosen the fastening of the fastened body 1, the steel ball 5 will be gripped by the screw thread of the bolt and the slope of the nut and therefore the rotation of the nut will be perfectly prevented. In case it is necessary to loosen the screw, if the steel ball 5 is moved in the direction reverse to that of the above described case, for example, by using the screw driver 7, the above described locking effect will be able to be easily overcome.

As explained above, according to the present invention, the slope 4 is formed on the edge of the aperture of the female screw and the ball 5 is fitted between the said slope and both walls of the groove of the male screw thread. Thus, when the screw tends ot rotate due to vibration or the like, the ball 5 will be gripped and therefore loosening If the driver 7 is further rotated, as

Therefore, the

can be positively prevented. Further, as the ball 5 remains pressed in the male screw thread, it is not likely to drop and can be easily removed. Further, as only one small ball is required for the device, the price is very low. At the same time, as the small ball is embedded in the threaded part'of the screw, no extra space for the locking device is required at all.

In the present invention, the bolt, nut and ball are not always necessarily made of iron or steel. Even if the a bolt and nut are made, for example, of plastics, the same effect will be obtained. However, it is needless to say that, in such case, the ball should be made of plastic harder than that of the bolt and nut.

The foregoing description relates to the case in which both bolt and nut are provided with threads. In the case Where, as shown in FIGURE 7, a nut 14 consisting of a threaded portion 12 and an unthreaded portion 13 is screwed onto a bolt 2 above a body 1 to be fastened, the locking action of the present device can be-efiected similarly by forming a slope 16 on an edge of the unthreaded portion 13 and fitting a ball 17 against said slope.

The screw driver 7 according to the present invention as shown in FIGURE 3 is conveniently applied to the bolt having an end extended outwardly. However, in case an end of the bolt is not extended so much, a screw driver as shown in FIGURE 8 may be used. The screw driver 18 is of a cylindrical shape providing with a conical part 19 at an extreme end thereof and threads 20 on its cylindrical inner surface. The cylindrical outer end of said screw driver is formed partially with a cut-off portion 21 and another part of said cylindrical outer end is formed so that the outer and remains flat over a length of about /2'n' from said cut-off portion 21, along said conical part 19, so as to form a projection 24,,and the rest of the outer end is cut along a line 22 connecting an end of said projection 24 with a point opposite and corresponding to the base of said cut-off portion 21.

Thus, as described above, the ball 23 may be pressed into the slope by meshing threads 20 of the screw driver 18 with threads of the bolt. When unscrewing the screw driver 18, the end of the driver 18 is elevated along the line 22 while the ball 23 remains where it is, so that only the driver may be disengaged.

What is claimed is:'

A screw locking device for preventing relative rotation between parts provided respectively with cooperating male and female threads, said latter part having a conically sloping surface at an end of its threaded aperture, comprising a ball fitted between and contacting said sloping surface and both Walls of a male thread groove, the inclination of said surface and said groove walls being such that an imaginary straight line, passing through the point of contact between the ball and said surface and through the center of said ball, passes between the points of contact between said ball and said groove walls.

References (Jited by the Examiner UNITED STATES PATENTS 527,569 10/94 Weisell 8110 X 669,608 3/01 Williams 81--1O 855,779 6/07 Hinkle. 1,058,295 4/ 13 Faucher 81-40 1,110,957 9/14 McGehee. 1,386,259 8/21 Jourdan et a1. 1,397,876 11/21 Meldal. 1,470,528 10/23 Flentjen 8190 X 1,480,811 1/24 Baron et a1. 8110 2,103,944 12/37 Gullborg.

WILLIAM FELDMAN, Prirmzry Examiner.

MILTON S. MEI-IR, Examiner. 

